Regional NRM Strategy

Climate Change

Overwhelming scientific evidence suggests that the climate within the Wheatbelt (Avon) NRM Region is changing, and will continue to change, most likely for generations into the future. It is clear that South West WA has experienced a decline in rainfall since the 1970s, and these trends in declining rainfall are generally consistent with modelled scenarios for climate change for the region.

Climate Change in the South West WA

Recent research has found that weather patterns in South West WA have already changed, including a decrease in autumn and winter rainfall (and associated increase in the prevalence of high pressure systems) and increased drought conditions. The signal of rainfall decline in South West WA is considered exceedingly robust. The most recent climate modelling strongly suggests that large-scale atmospheric changes associated with South West WA rainfall reductions are consistent with those expected from atmospheric impacts associated with increased greenhouse gas concentrations.

Our changing climate will result in a range of environmental and socio-economic consequences, including changes to agricultural productivity, water resources and loss of biodiversity and associated environmental impacts. Understanding the flow-on effects of these changes on local communities, economics, industry and infrastructure is critical to help communities adapt to a changing climate and remain viable.

Climate change projections

Climate change projections show how climate may change in the future. There are a range of things to consider when relying on climate change projections to help formulate your natural resource management decisions. For a full discussion of the CSIRO climate change projections, please see the Climate Change in Australia website.

Climate Change: Rainfall (growing season)

Climate Change: Rainfall (summer)

Description

The layers presented in the maps are derived from two main sources, the CSIRO Climate Change in Australia Map Explorer and the Bureau of Meteorology average temperature variables dataset. Projected rainfall data are based on the model choices, climate change scenarios and timeframes described here while the historical values represent the average over the standard 30 year period from 1961-1990.

Regional analysis

The whole region is projected to receive less annual rainfall; under high emission scenarios to the year 2070, the region’s annual rainfall is projected to decrease by 24% (85 mm); growing season rainfall decrease by 50% (133 mm) and summer rainfall by 8% (4 mm).

High emissions do not necessarily project a greater rate of change in rainfall; likely due to the range of factors that influence rainfall; and

Summer rainfall will be stable in the short term but decrease in the longer-term.

Rainfall at a sub-regional analysis

The Southern sub-region has the highest projected decrease in summer rainfall under all scenarios;

Under low emissions, all except the Southern sub-region may experience stable or slightly increased summer rainfall; under high emissions, only the Great Western Woodlands are projected to show a slight increase in summer rainfall in the short term (to 2030).

Projections suggest a greater decrease in growing season rainfall in the short term under low emissions scenarios; the effect is greatest in the Avon Arc than the long-term.

Table 2. The average annual, growing season and summer rainfall by sub-region.

Climate Change: Temperature (Summer max)

Climate Change: Temperature (Winter min)

The layers presented in the maps are derived from two main sources; projected climate data come from the CSIRO Climate Change in Australia Map Explorer; and historical climate data from the Australian Bureau of Meteorology average temperature variables dataset. Projected climate data are based on the model choices, climate change scenarios and timeframes described here while the historical values represent the average, maximum and minimum temperatures over the standard 30 year period from 1961-1990.

Temperature at a regional analysis

The whole region is projected to get warmer; by up to 2oC to the year 2070.

The rate of change is fastest in the 15 years up to 2030.

There is small but significant difference between the projected temperature change under medium and high emissions scenarios under both timeframes.

The historic average annual temperature of approx. 17oC is projected to increase by 1oC to 2030 and 2oC by 2070 under medium and high emission scenarios.

The mean maximum summer temperatures are projected to increase by up to 3oC and mean minimum winter temperatures increase up to 1.7oC.

The range of annual and summer temperatures is projected to stay relatively stable however the winter temperatures are projected to get less variable at a regional scale.

There is a projected increase in both summer maximum and winter minimum temperatures for all sub-regions; and the range between these extremes will get larger over the next 15 years but be most pronounced in the central sub-region and least pronounced in the Great Western Woodlands. In the longer term, the range between extremes is projected to decrease.

Historically the Eastern sub-region has the highest mean annual maximum temperatures and is consistently projected to have the highest increases in mean annual temperature of up to 2.6oC under high emissions to 2070. Mean maximum summer temperatures are projected to reach 35-36oC by 2070; which is approx. 2.3-3.3 degrees hotter than current means.

The Southern sub-region has the “coolest” annual and summer temperatures with the lowest projected increases in temperatures, except in winter when the minimum temperatures are projected to increase by up to 1.82oC under high emissions to 2070. It will remain a relatively cool region but the winters will get significantly warmer.

The Central region consistently shows the highest projected increase in summer maximums of up 3.27oC under moderate emissions to 2070 and also has the warmest projected minimum winter temperatures.

While it is historically one of the coolest sub-regions in winter, the Great Western Woodlands show the greatest increases in winter minimum temperature increasing from the current by 2.24oC under high emission to 2070.

The Avon Arc consistently represents intermediate historical and projected temperatures between the “cool” Southern sub-region and the mean warmer sub-regions to its east; however it shows the lowest projected increases in winter minimums under most scenarios.

Table 4. The historical and projected average annual, summer maximum and winter minimum temperatures by sub-region.